Convert a PPM image to an arbitrary text format according to a template. More information: https://netpbm.sourceforge.net/doc/ppmtoarbtxt.html.
ppmtoarbtxt path/to/template path/to/image.ppm > path/to/output_file.txt
ppmtoarbtxt path/to/template -hd path/to/head_template path/to/image.ppm > path/to/output_file.txt
ppmtoarbtxt path/to/template -hd path/to/tail_template path/to/image.ppm > path/to/output_file.txt
ppmtoarbtxt -version